U.S. Pat. No. 4,395,109 describes a roller fusing mechanism for fusing toner to paper or another substrate in which a thin resistive heating layer connectable to an electrical power supply is positioned close to the surface of a fusing roller. The resistive heating layer is insulated from a metal core and is covered by a protective layer having an abhesive fusing surface. This type of structure permits the heat generated within the resistive heating layer to be conducted rapidly and efficiently to the fusing surface. Consequently, the surface temperature can be controlled more accurately and the power requirement for the fusing mechanism is reduced.
In this prior structure, electrical contact is provided to the resistive heating layer by copper conductive elements of substantial thickness positioned on the surface of the roller in a location at which the resistive heating layer is uncovered by the protective layer. These conductive elements are electrically contacted as the roller rotates, by brushes or the like connected to the power supply.
Sizeable conductive elements of this type are readily contactable, but interfere with other aspects of the apparatus. For example, most fusing rollers need the application of a release oil to prevent offset of toner in operation. Oil can corrode the conductive elements and the elements themselves can provide a conduit for oil to travel deeper into the roller where it can cause damage.